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Advanced Defensive Stats: Coverage

| July 9th, 2020

I’m continuing to look at Chicago’s defense using advanced defensive statistics from Pro Football Reference (PFR). I already looked at missed tackles, and today I want to look at coverage.


Baseline Rates

There are a whole host of advanced coverage stats available, including completion percentage, yards/target, target depth, yards after catch allowed, TDs, INTs, and passer rating. In order to keep it simple, I’m going to look only at yards/target, as that is a good baseline metric for how effective teams are when targeting a player. I’m intentionally not looking at passer rating because that gets skewed by touchdowns and interceptions, which are notoriously random statistics within a small sample size like this.

I compiled all yards/target stats from the PFR database for 2018 and 2019, the only 2 years it has, and sorted them by position. In order to compare starters to starters and avoid rates skewed by backups, I assumed a base nickel package of 4 defensive linemen (DL), 2 linebackers (LB), 3 cornerbacks (CB), and 2 safeties (S). For all 32 teams over a 2 year span, this would mean 128 LB, 192 CB, and 128 S. This gave thresholds of 30 targets for LB, 40 for CB, and 20 for S.

Looking at those sample sizes, you can see the spread of missed tackle rates in the table below for each position group.

A few thoughts:

  • Generally, safeties give up the highest yards/target while linebackers give up the lowest mark. This makes sense considering where each is targeted.
  • Unlike with missed tackles, the average and median (middle) are fairly close together here, indicating that there is a fairly normal distribution of values.

I should note that I looked at how these rates compared for individuals from 2018 to 2019 and found very little relationship. It’s hard to say with only 2 years’ worth of data, but it doesn’t look like missed tackle rate is super consistent from year to year. For the 120 players with at least 40 targets in both 2018 and 2019, the correlation of 2018 yards/target vs. 2019 yards/target was only 0.073, indicating a weak relationship. However, 58 of those 120 were either above or below average both years (32 above, 26 below). So while there is definitely fluctuation, there might be some sort of trend consistency for many players. It’s really too early to say for sure.

Now let’s go through one position group at a time to see how the Bears’ main players fared in 2019.


CB

We’ll start at corner. The table below shows how all Chicago’s main 2019 CBs fared, as well as players signed from other teams who will be on the Bears in 2020. I included some of the depth pieces, but not their percentages, because the sample sizes are too small to mean much. I also included 2018 information for anybody who had it and color coded their percentile range to match the table above.

A few thoughts:

  • For the 3rd year in a row, Kyle Fuller was among the most heavily targeted players in the NFL. Unlike in 2017 and 2018 however, he did not hold up well when targeted. Fuller very much needs to have a bounce back season in 2020.
  • Prince Amukamara also saw his performance take a significant dip in 2019. It’s difficult for rookie CB to play well, but thankfully Jaylon Johnson doesn’t have to play at an overly high level to match Prince’s 2019 production.
  • If Fuller of Johnson get hurt, there is little reason to be excited about Chicago’s CB depth on the outside. Artie Burns was terrible in Pittsburgh (albeit in a small sample size), and Kevin Toliver has been below average through 2 years in Chicago; if you combine his 2 years into one sample, you get 8.5 yards/target on 34 targets, which would be in the bottom 30% of CBs.
  • In the slot, Buster Skrine had a strong 2019 season in coverage after being around average in 2018. I’m tempted to think this might be a function of him being in the slot, but a study I did after the Bears signed him last off-season found that well-respected nickel CBs gave up an average of 7.4 yards/target in 2018, which is similar to all CBs here. Skrine struggles a bit in run support, but is a good solid coverage player.

Safety

Let’s move on to safety now. The table below shows how their key players fared in 2019, plus newcomers who were signed for 2020. Color coding matches the table above.

A few thoughts:

  • Hello, Eddie Jackson! While he might struggle with missed tackles, he’s been consistently excellent in coverage over the last two years.
  • HaHa Clinton-Dix struggled between GB and Washington in 2018, but played quite well in Chicago in 2019. The Bears can only hope Tashaun Gipson improves in a similar manner as he moves over from Houston. He wasn’t bad in coverage in 2019, but he wasn’t particularly good either.
  • Should either of the starters get hurt, the Bears have to feel pretty good about Deon Bush as the third safety. Bush has held up pretty well (though admittedly in a small sample size) both in coverage and as a tackler when forced into action over the last two years.

Linebacker

Finally, let’s look at the linebackers. Khalil Mack and Robert Quinn haven’t gotten enough targets to warrant talking about (they have combined for 19 total targets in the last 2 seasons), so we’ll mainly look at the inside linebackers, though I do include Leonard Floyd and Barkevious Mingo as OLBs who provide more coverage ability.

A few thoughts:

  • Roquan Smith showed significant improvement in coverage from his rookie season, and Bears fans can only hope that was a sign of growth, not an aberration.
  • Danny Trevathan, on the other hand, took a nosedive in coverage, though some of that might be a due to a smallish sample size before he got hurt. Given that the Bears just gave him an incredibly backloaded three year contract, they need to hope he plays well for at least the next two seasons.
  • Nick Kwiatkoski and Kevin Pierre-Louis were outstanding in coverage after Trevathan and Smith got hurt last year. Current top backup Devante Bond does not have much of a track record in coverage, but he struggled there in a limited sample size in TB in 2018. ILB depth remains a big area of concern for the Bears.
  • At OLB, Leonard Floyd was consistently strong in coverage the last two years. Neither Mack nor Quinn should be expected to drop into coverage as often as Floyd did, and I anticipate Barkevious Mingo being the OLB who will get snaps when the Bears want more coverage options. He wasn’t particularly good in coverage in Seattle in 2018. Considering Mingo also offers next to nothing as a pass rusher, OLB depth is also an area of concern for the Bears.

Lessons Learned

At cornerback, Kyle Fuller looks to bounce back from a down year, while Buster Skrine will attempt to maintain his strong performance from 2019. The Bears need to hope Jaylon Johnson grabs the starting spot and plays well, because depth options Kevin Toliver and Artie Burns don’t inspire much confidence based on their past performances.

At safety, Eddie Jackson is fantastic, and Tashaun Gipson should be solid, but appears to be a coverage downgrade from HaHa Clinton-Dix. Deon Bush has been respectable in coverage in limited action the last two years and provides the Bears with solid depth.

At linebacker, the Bears should feel good about Roquan Smith in coverage, but Danny Trevathan needs to show a down 2019 (prior to injury) was an aberration and not a sign of things to come. Losing Leonard Floyd’s strong coverage abilities at the OLB spot will hurt the Bears’ scheme versatility, and depth looks to be a serious concern across the board.

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